"The avatāra, or incarnation of Godhead, descends from the kingdom of God for material manifestation. And the particular form of the Personality of Godhead who so descends is called an incarnation, or avatāra. Such incarnations are situated in the spiritual world, the kingdom of God. When they descend to the material creation, they assume the name avatāra."
(Bhagavad-Gita-----4:8-----purport).

According to Bhagavad-gītā this atheistic conclusion is false. In the verse under discussion it is stated that Kṛṣṇa is the original cause of the material manifestation. Śrīmad-Bhāgavatam also confirms this. The ingredients of the material manifestation are separated energies of the Lord. Even the brahma-jyotir, which is the ultimate goal of the impersonalists, is a spiritual energy manifested in the spiritual sky. There are no spiritual diversities in the brahma-jyotir as there are in the Vaikuṇṭhalokas, and the impersonalist accepts this brahma-jyotir as the ultimate eternal goal. The Paramātmā manifestation is also a temporary all-pervasive aspect of the Kṣīrodakaśāyī Viṣṇu. The Paramātmā manifestation is not eternal in the spiritual world. Therefore the factual Absolute Truth is the Supreme Personality of Godhead Kṛṣṇa. He is the complete energetic person, and He possesses different separated and internal energies.
(Bhagavad-Gita-----7:4-----purport).

Yet one should not conclude that because He is spread all over He has lost His personal existence. To refute such an argument the Lord says, "I am everywhere, and everything is in Me, but still I am aloof." For example, a king heads a government which is but the manifestation of the king's energy; the different governmental departments are nothing but the energies of the king, and each department is resting on the king's power. But still one cannot expect the king to be present in every department personally. That is a crude example. Similarly, all the manifestations that we see and everything that exists, both in this material world and in the spiritual world, are resting on the energy of the Supreme Personality of Godhead. The creation takes place by the diffusion of His different energies, and, as stated in the Bhagavad-gītā, viṣṭabhyāham idaṁ kṛtsnam: He is everywhere present by His personal representation, the diffusion of His different energies.
(Bhagavad-Gita-----9:4-----purport).

The impersonalist or pantheist cannot understand the exceptional opulences of the Supreme Lord nor the manifestations of His divine energies. Both in the material world and in the spiritual world His energies are distributed in every variety of manifestation. Now Kṛṣṇa is describing what can be directly perceived by the common man; thus part of His variegated energy is described in this way.
(Bhagavad-Gita-----10:19-----purport).

Everything is resting on the Supreme Personality of Godhead; therefore He is the ultimate rest. Nidhānam means that everything, even the Brahman effulgence, rests on the Supreme Personality of Godhead, Kṛṣṇa. He is the knower of everything that is happening in this world, and if knowledge has any end, He is the end of all knowledge; therefore He is the known and the knowable. He is the object of knowledge because He is all-pervading. Because He is the cause in the spiritual world, He is transcendental. He is also the chief personality in the transcendental world.
(Bhagavad-Gita-----11:38-----purport).

And so, factually, there are two classes of transcendentalists. Now Arjuna is trying to settle the question of which process is easier and which of the classes is most perfect. In other words, he is clarifying his own position because he is attached to the personal form of Kṛṣṇa. He is not attached to the impersonal Brahman. He wants to know whether his position is secure. The impersonal manifestation, either in this material world or in the spiritual world of the Supreme Lord, is a problem for meditation. Actually, one cannot perfectly conceive of the impersonal feature of the Absolute Truth. Therefore Arjuna wants to say, "What is the use of such a waste of time?" Arjuna experienced in the Eleventh Chapter that to be attached to the personal form of Kṛṣṇa is best because he could thus understand all other forms at the same time and there was no disturbance to his love for Kṛṣṇa. This important question asked of Kṛṣṇa by Arjuna will clarify the distinction between the impersonal and personal conceptions of the Absolute Truth.
(Bhagavad-Gita-----12:1-----purport).

Similarly, the living entities are also in Him, and because they are conditioned, they are averse to serving the Supreme Lord. Thus they are not allowed to enter into the spiritual sky. But with the coming forth of material nature these living entities are again given a chance to act in the material world and prepare themselves to enter into the spiritual world. That is the mystery of this material creation. Actually the living entity is originally the spiritual part and parcel of the Supreme Lord, but due to his rebellious nature, he is conditioned within material nature. It really does not matter how these living entities or superior entities of the Supreme Lord have come in contact with material nature. The Supreme Personality of Godhead knows, however, how and why this actually took place. In the scriptures the Lord says that those attracted by this material nature are undergoing a hard struggle for existence. But we should know it with certainty from the descriptions of these few verses that all transformations and influences of material nature by the three modes are also productions of material nature. All transformations and variety in respect to living entities are due to the body. As far as spirit is concerned, living entities are all the same.
(Bhagavad-Gita-----13:20-----purport).

This tree, being the reflection of the real tree, is an exact replica. Everything is there in the spiritual world. The impersonalists take Brahman to be the root of this material tree, and from the root, according to Sāṅkhya philosophy, come prakṛti, puruṣa, then the three guṇas, then the five gross elements (pañca-mahā-bhūta), then the ten senses (daśendriya), mind, etc. In this way they divide up the whole material world into twenty-four elements. If Brahman is the center of all manifestations, then this material world is a manifestation of the center by 180 degrees, and the other 180 degrees constitute the spiritual world. The material world is the perverted reflection, so the spiritual world must have the same variegatedness, but in reality.
(Bhagavad-Gita-----15:1-----purport).

The following information is there in the Mādhyandināyana-śruti: sa vā eṣa brahma-niṣṭhā idaṁ śarīraṁ martyam atisṛjya brahmābhisampadya brahmaṇā paśyati brahmaṇā śṛṇoti brahmaṇaivedaṁ sarvam anubhavati. It is stated here that when a living entity gives up this material embodiment and enters into the spiritual world, he revives his spiritual body, and in his spiritual body he can see the Supreme Personality of Godhead face to face. He can hear and speak to Him face to face, and he can understand the Supreme Personality as He is. From smṛti also it is understood, vasanti yatra puruṣāḥ sarve vaikuṇṭha-mūrtayaḥ: in the spiritual planets everyone lives in bodies featured like the Supreme Personality of Godhead's. As far as bodily construction is concerned, there is no difference between the part-and-parcel living entities and the expansions of viṣṇu-mūrti. In other words, at liberation the living entity gets a spiritual body by the grace of the Supreme Personality of Godhead.
(Bhagavad-Gita-----15:7-----purport).

According to the statement of the Supreme Personality of Godhead, Lord Kṛṣṇa, there are two classes of living entities. The Vedas give evidence of this, so there is no doubt about it. The living entities who are struggling in this world with the mind and five senses have their material bodies, which are changing. As long as a living entity is conditioned, his body changes due to contact with matter; matter is changing, so the living entity appears to be changing. But in the spiritual world the body is not made of matter; therefore there is no change. In the material world the living entity undergoes six changes—birth, growth, duration, reproduction, then dwindling and vanishing. These are the changes of the material body. Butin the spiritual world the body does not change; there is no old age, there is no birth, there is no death. There all exists in oneness. Kṣaraḥ sarvāṇi bhūtāni: any living entity who has come in contact with matter, beginning from the first created being, Brahmā, down to a small ant, is changing its body; therefore they are all fallible. In the spiritual world, however, they are always liberated in oneness.
(Bhagavad-Gita-----15:16-----purport).